Mineral spirits, a hydrocarbon solvent derived from crude oil, is perhaps the most commonly known paint thinner, especially for oil-based paint. Mineral spirits is also commonly used in paint cleanup for the tools and other surfaces used in painting with oil-based and latex-based paint. Because of its direct relation to crude oil, mineral spirits is subject to fluctuations in the price of crude oil, such fluctuations often being upward.
As local, state and federal governments require stricter controls on the amount of volatile organic compounds and combustible chemicals which can be used, the compositions used to thin paint often must be changed to comply with those controls.
Another commonly used paint thinner is turpentine. However, in contrast to mineral spirits, turpentine typically leaves a gummy residue, tends to deteriorate with age and is generally more expensive.
Paint thinner compositions which are predominantly or entirely composed of mineral spirits or turpentine may create safety and storage concerns, as these two materials are highly combustible.
Biodegradability may also be a concern for current paint thinner compositions which are predominantly or entirely composed of mineral spirits.
In addition, when working with paint thinner compositions, the user must also be concerned about the disposal of hazardous substances and the use of non-renewable resources. These two concerns are becoming more important as environmental issues become more significant.
One such known paint thinner is a water containing macroemulsion used for the thinning and clean-up of paint. See copending Application Publication Nos. 2007/0135325, 2009/0200516 and 2009/0211492, entire disclosures of which are incorporated herein by reference.
The macroemulsions contain particle sizes of the internal phase in the range of the wavelength of visible light. Known macroemulsions may achieve thinning results and clean up performance as well as containing a low solids level in order to prevent interference with the physical and chemical properties of the thinned paint, the macroemulsions have at least three major drawbacks. First, since macroemulsions scatter visible light, macroemulsions have the drawback of being opaque or hazy and can tend to hide the cleaning process to the point that the end user cannot tell when equipment or brushes are clean. Secondly, macroemulsions are typically not thermodynamically stable and will separate with time causing a non-uniform presence in the container. This can cause the user to use too much of one phase or less of another when using the product over time. This can affect performance depending on the separation, requiring the user to shake well before using. Thirdly, macroemulsions typically have considerably low performance compared to the traditional hydrocarbon solvents, being up to three times less effective.
Microemulsions are well known in the cleaning and other industries. These typical microemulsions are not suitable for thinning paint. The known microemulsions typically require a high solids load, for example, surfactants, in order to dissolve the thinning agent into a microemulsion. This high solids load typically causes two problems. One, high solids in a paint thinner, when the paint thinner is added to the paint in quantities necessary to thin the paint, usually can cause adverse effects on the chemical and/or physical properties of the paint. These include changes in gloss, dry time, paint film defects, hardness and color. Secondly, at this high level of surfactants, cost can be two to three times higher than either macroemulsions or straight hydrocarbons.
There is a need in the industry for a paint thinner composition for oil-based paint in which the composition eliminates or minimizes the disadvantages or problems encountered with the known compositions.